US9919687B2 - Hydraulic braking system - Google Patents

Hydraulic braking system Download PDF

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Publication number
US9919687B2
US9919687B2 US14/902,664 US201414902664A US9919687B2 US 9919687 B2 US9919687 B2 US 9919687B2 US 201414902664 A US201414902664 A US 201414902664A US 9919687 B2 US9919687 B2 US 9919687B2
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pressure
hydraulic
chamber
control
linear valve
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US20160200301A1 (en
Inventor
Yusuke KAMIYA
Masaaki Komazawa
Kiyoyuki Uchida
Masaki Ninoyu
Akitaka Nishio
Masaki Maruyama
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Advics Co Ltd
Toyota Motor Corp
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Advics Co Ltd
Toyota Motor Corp
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Assigned to ADVICS CO., LTD., TOYOTA JIDOSHA KABUSHIKI KAISHA reassignment ADVICS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MARUYAMA, MASAKI, NISHIO, AKITAKA, NINOYU, MASAKI, KAMIYA, YUSUKE, UCHIDA, KIYOYUKI, KOMAZAWA, MASAAKI
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T7/00—Brake-action initiating means
    • B60T7/02—Brake-action initiating means for personal initiation
    • B60T7/04—Brake-action initiating means for personal initiation foot actuated
    • B60T7/042—Brake-action initiating means for personal initiation foot actuated by electrical means, e.g. using travel or force sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T1/00—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles
    • B60T1/02—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels
    • B60T1/10—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels by utilising wheel movement for accumulating energy, e.g. driving air compressors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/12—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being liquid
    • B60T13/14—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being liquid using accumulators or reservoirs fed by pumps
    • B60T13/142—Systems with master cylinder
    • B60T13/145—Master cylinder integrated or hydraulically coupled with booster
    • B60T13/146—Part of the system directly actuated by booster pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/66—Electrical control in fluid-pressure brake systems
    • B60T13/662—Electrical control in fluid-pressure brake systems characterised by specified functions of the control system components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/66—Electrical control in fluid-pressure brake systems
    • B60T13/68—Electrical control in fluid-pressure brake systems by electrically-controlled valves
    • B60T13/686—Electrical control in fluid-pressure brake systems by electrically-controlled valves in hydraulic systems or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/40—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition comprising an additional fluid circuit including fluid pressurising means for modifying the pressure of the braking fluid, e.g. including wheel driven pumps for detecting a speed condition, or pumps which are controlled by means independent of the braking system
    • B60T8/4072—Systems in which a driver input signal is used as a control signal for the additional fluid circuit which is normally used for braking
    • B60T8/4077—Systems in which the booster is used as an auxiliary pressure source
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/40—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition comprising an additional fluid circuit including fluid pressurising means for modifying the pressure of the braking fluid, e.g. including wheel driven pumps for detecting a speed condition, or pumps which are controlled by means independent of the braking system
    • B60T8/4072—Systems in which a driver input signal is used as a control signal for the additional fluid circuit which is normally used for braking
    • B60T8/4081—Systems with stroke simulating devices for driver input
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/42—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition having expanding chambers for controlling pressure, i.e. closed systems
    • B60T8/4275—Pump-back systems
    • B60T8/4291—Pump-back systems having means to reduce or eliminate pedal kick-back
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D61/00—Brakes with means for making the energy absorbed available for use
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2270/00—Further aspects of brake control systems not otherwise provided for
    • B60T2270/60—Regenerative braking
    • B60T2270/604—Merging friction therewith; Adjusting their repartition

Definitions

  • the present invention relates to suppression of a vibration of a hydraulic pressure in a hydraulic braking system.
  • Patent Document 1 discloses a hydraulic braking system including (i) a plurality of brake cylinders, (ii) a high pressure source including a pump device, (iii) a common passage to which the plurality of brake cylinders and the high pressure source are connected, (iv) a master cylinder connected to brake cylinders for front left and right wheels via respective master cut-off valves, (v) a pressure-increase linear valve and a pressure-reduction linear valve configured to control a hydraulic pressure in the common passage, and (iv) an anti-lock control valve device provided between the common passage and the plurality of brake cylinders and including a plurality of anti-lock control valves.
  • the pressure-increase linear valve and the pressure-reduction linear valve are controlled to control the hydraulic pressure in the common passage to control hydraulic pressures in the respective plurality of brake cylinders in common.
  • the pressure-increase linear valve and the pressure-reduction linear valve control the hydraulic pressure in the common passage
  • the plurality of anti-lock control valves control the hydraulic pressures in the respective brake cylinders, individually, but an opening and closing switching pressure of each of the pressure-increase linear valve and the pressure-reduction linear valve is greater than in the normal braking.
  • the pressure-increase linear valve is opened, and the pressure-reduction linear valve is closed, thereby suppressing change in the hydraulic pressure in the common passage due to opening and closing operations of the anti-lock control valves.
  • Patent Document 1 JP-A-2012-192767
  • the object of the present invention is to suppress vibrations of a hydraulic pressure in an upstream portion located upstream of a slip control device in a hydraulic braking system.
  • the invention of the present application relates to a hydraulic braking system including a slip control device configured to control hydraulic pressures in respective brake cylinders to control a slipping state of each wheel.
  • a hydraulic-pressure producing device controls a hydraulic pressure in an upstream portion located upstream of the slip control device and suppresses vibrations of the hydraulic pressure in the upstream portion.
  • This suppression of the vibrations of the hydraulic pressure in the upstream portion can reduce lowering in accuracy of control of the slip control device for the hydraulic pressures in respective brake cylinders.
  • a hydraulic braking system comprising:
  • a slip control device provided between the hydraulic-pressure producing device and the plurality of brake cylinders and configured to control a hydraulic pressure in each of at least one of the plurality of brake cylinders to control a slipping state of each of the plurality of wheels
  • the hydraulic-pressure producing device comprising a stiffness reducer configured to reduce stiffness in an upstream portion located upstream of the slip control device such that the stiffness is less in a case where the slip control device is in an operating state than in a case where the slip control device is in a non-operating state.
  • Reduction in the stiffness in the upstream portion can absorb vibrations due to operations of the slip control device, resulting in suppression of the vibrations.
  • the volume of the upstream portion is more easily changed with a small force in the case where the stiffness K is low than in the case where the stiffness K is high, so that the vibrations are more easily absorbed.
  • the stiffness in the upstream portion is reduced, thereby well absorbing the vibrations due to the operations of the slip control device.
  • the slip control device may individually control the respective hydraulic pressures in the plurality of brake cylinders and may control the respective hydraulic pressures in the two brake cylinders in common.
  • the hydraulic-pressure producing device comprises (i) a master cylinder comprising (a) a pressurizing piston fluid-tightly and slidably fitted in a housing, (b) a front pressure chamber provided in front of the pressurizing piston and connected to the upstream portion, and (c) a rearward chamber provided at a rear of the pressurizing piston, and (ii) a rear-hydraulic-pressure control device capable of controlling a hydraulic pressure in the rearward chamber, and
  • stiffness reducer comprises a rearward chamber stiffness reducer configured to reduce stiffness in the rearward chamber to reduce stiffness in the front pressure chamber, and the rearward chamber stiffness reducer is comprised in the rear-hydraulic-pressure control device.
  • the hydraulic pressure in the front pressure chamber is vibrated with vibrations of a hydraulic pressure in the upstream portion.
  • the vibrations of the hydraulic pressure in the front pressure chamber are transmitted to the rearward chamber via the pressurizing piston. Accordingly, reduction in stiffness of the rearward chamber can reduce stiffness in the front pressure chamber, resulting in reduction in the stiffness in the upstream portion.
  • front pressure chamber and the upstream portion may be connected to each other in a state in which the front pressure chamber and the upstream portion always communicate with each other and may be connected to each other in a state in which communication and isolation between the front pressure chamber and the upstream portion are switchable.
  • rear-hydraulic-pressure control device comprises:
  • the rearward chamber stiffness reducer comprises a control-pressure-chamber stiffness reducer configured to control one or more of at least one of the pressure-increase linear valve and the pressure-reduction linear valve to reduce stiffness in the control pressure chamber such that the stiffness in the control pressure chamber is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state, and the control-pressure-chamber stiffness reducer is comprised in the control-pressure-chamber hydraulic pressure controller.
  • Vibrations of the hydraulic pressure in the rearward chamber are transmitted to the servo chamber and then to the control pressure chamber via the control piston. Accordingly, reduction in the stiffness in the control pressure chamber can suppress vibrations of hydraulic pressures in the servo chamber and the rearward chamber, resulting in suppression of the vibrations of the hydraulic pressures in the front pressure chamber and the upstream portion.
  • the hydraulic pressure in the rearward chamber and the hydraulic pressure in the servo chamber are made substantially equal to each other, so that a relationship determined by, e.g., a construction of the regulator is established between the hydraulic pressure in the servo chamber and the hydraulic pressure in the control pressure chamber.
  • the hydraulic pressure in the rearward chamber and the hydraulic pressure in the control pressure chamber have a one-to-one relationship. Accordingly, by controlling an actual hydraulic pressure in the control pressure chamber such that the actual hydraulic pressure in the control pressure chamber is brought closer to its target hydraulic pressure, an actual hydraulic pressure in the rearward chamber can be brought closer to its target hydraulic pressure. It is noted that the hydraulic pressure in the servo chamber and the hydraulic pressure in the control pressure chamber may be made substantially equal to each other.
  • a power hydraulic pressure source may be used as the high pressure source.
  • the power hydraulic pressure source may be constituted by a pump device and an accumulator.
  • the rear-hydraulic-pressure control device comprises a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source
  • the pressure-reduction linear valve comprises a characteristic in which a valve opening current is less in a case where a pressure differential between the control pressure chamber and the low pressure source is small than in a case where the pressure differential between the control pressure chamber and the low pressure source is large, and
  • control-pressure-chamber stiffness reducer comprises a pressure-reduction-linear-valve current controller configured to reduce a current to be supplied to a coil of the pressure-reduction linear valve such that the current is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • the current to be supplied to the coil of the pressure-reduction linear valve is determined so as to be less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state. Even when the pressure differential is small, an open state of the pressure-reduction linear valve is established, and accordingly the pressure-reduction linear valve tends to be open. As a result, the change in volume of the control pressure chamber is allowed in a greater degree in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state. This allowance of the change can reduce the stiffness.
  • the rear-hydraulic-pressure control device comprises a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source
  • the pressure-reduction linear valve is configured to be in an open state when the hydraulic pressure in the control pressure chamber is greater than an opening and closing switching pressure in a state in which the current to be supplied to a coil of the pressure-reduction linear valve is kept, and the opening and closing switching pressure is determined by the current to be supplied to the coil of the pressure-reduction linear valve, and
  • control-pressure-chamber stiffness reducer comprises a pressure-reduction linear valve controller configured to reduce the opening and closing switching pressure such that the opening and closing switching pressure is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • a relationship of a position of a valve member relative to a valve seat is determined based on a relationship among a pressure differential force Fp, an elastic force Fs of a spring, and an electromagnetic driving force Fd.
  • the pressure differential force Fp is related to a pressure differential between a high pressure side and a low pressure side of the electromagnetic valve.
  • the electromagnetic driving force Fd is related to a current to be supplied to the coil. In the case where a hydraulic pressure of the low pressure source is constant, the pressure differential force Fp acting on the pressure-reduction linear valve as the electromagnetic valve is greater in the case where the hydraulic pressure in the control pressure chamber is high than in the case where the hydraulic pressure in the control pressure chamber is low.
  • the pressure-reduction linear valve is a normally open valve
  • the elastic force Fs of the spring acts on the valve member in a direction in which the valve member is moved away from the valve seat, and when the electromagnetic driving force Fd exceeds the sum of the pressure differential force and the elastic force of the spring, the pressure-reduction linear valve is switched to its closed state (Fd>Fs+Fp: closed).
  • the pressure-reduction linear valve is a normally closed valve
  • the elastic force Fs of the spring acts on the valve member in a direction in which the valve member is seated on the valve seat, and when the sum of the electromagnetic driving force Fd and the pressure differential force Fp exceeds the elastic force Fs of the spring, the pressure-reduction linear valve is switched to the open state (Fd+Fp>Fs: open).
  • the pressure-reduction linear valve is any of the normally open valve and the normally closed valve, in a period in which the hydraulic pressure in the control pressure chamber is higher than the opening and closing switching pressure determined by the supply current, the pressure-reduction linear valve is in the open state, so that the control pressure chamber communicates with the low pressure source.
  • the supply current is reduced to reduce the opening and closing switching pressure.
  • the pressure-reduction linear valve is the normally closed valve
  • the supply current is increased to reduce the opening and closing switching pressure.
  • the rear-hydraulic-pressure control device comprises a target hydraulic pressure determiner configured to determine a target hydraulic pressure in the control pressure chamber based on a brake request, and
  • the pressure-reduction linear valve controller comprises a target-hydraulic-pressure-change-based pressure-reduction linear valve controller configured to reduce the opening and closing switching pressure such that the opening and closing switching pressure is less in a case where a tendency of the target hydraulic pressure in the control pressure chamber is a decreasing tendency than in a case where the tendency of the target hydraulic pressure in the control pressure chamber is an increasing tendency.
  • the target hydraulic pressure may be determined, for example, based on the brake request determined based on a state of operation of a brake operating member by a driver. Also, in the case where an automatic brake is activated or in the case where traction control or vehicle stability control is executed, for example, the target hydraulic pressure may be determined based on a brake request which is determined by a request for activation of the automatic brake or a request in each control.
  • the control pressure chamber is fluidically coupled with the low pressure source more easily in the case where the target hydraulic pressure has the decreasing tendency than in the case where the target hydraulic pressure has the increasing tendency. This can well reduce the hydraulic pressure in the control pressure chamber so as to bring the hydraulic pressure in the control pressure chamber closer to the target hydraulic pressure.
  • the rear-hydraulic-pressure control device comprises a pressure-increase and pressure-reduction controller configured to compare an actual hydraulic pressure and a target hydraulic pressure in the control pressure chamber with each other to at least execute one of pressure-increase control for increasing the hydraulic pressure in the control pressure chamber and pressure-reduction control for reducing the hydraulic pressure in the control pressure chamber, and
  • the pressure-reduction linear valve controller is configured to reduce the opening and closing switching pressure such that the opening and closing switching pressure is less in a case where the pressure-reduction control is to be executed by the pressure-increase and pressure-reduction controller than in a case where the pressure-increase control is to be executed by the pressure-increase and pressure-reduction controller.
  • the pressure-increase and pressure-reduction controller may execute any one of the pressure-increase control and the pressure-reduction control and may be execute any one of the pressure-increase control, the pressure-reduction control, and holding control.
  • control pressure chamber may be directly detected by a sensor or other similar detectors and may be estimated based on, e.g., a control mode of each of the pressure-increase linear valve and the pressure-reduction linear valve.
  • the rear-hydraulic-pressure control device comprises (a) a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source and (b) a target-hydraulic-pressure-based pressure-reduction linear valve controller configured to control the pressure-reduction linear valve based on a target hydraulic pressure in the control pressure chamber, and
  • control-pressure-chamber stiffness reducer comprises a pressure-reduction-linear-valve-control target hydraulic pressure determiner configured to determine the target hydraulic pressure such that the target hydraulic pressure is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • the pressure-reduction linear valve in the open state when the actual hydraulic pressure in the control pressure chamber is greater than the target hydraulic pressure, and the pressure-reduction linear valve is switched to the closed state when the actual hydraulic pressure reaches the target hydraulic pressure, the pressure-reduction linear valve tends to be open when the target hydraulic pressure is set to a small value.
  • the rear-hydraulic-pressure control device comprises a pressure-increase linear valve provided between the control pressure chamber and a high pressure source
  • the pressure-increase linear valve comprises a characteristic in which a valve opening current and a pressure differential between the high pressure source and the control pressure chamber comprise a relationship in which the valve opening current decreases with increase in the pressure differential
  • control-pressure-chamber stiffness reducer comprises a pressure-increase linear valve controller configured to increase a current to be supplied, such that the current is greater in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • the current to be supplied to a coil of the pressure-increase linear valve is determined so as to be greater in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state. Even when the pressure differential is small, an open state of the pressure-increase linear valve is established, and accordingly the pressure-increase linear valve tends to be open. As a result, the change in volume of the control pressure chamber is allowed in a greater degree in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state. This allowance of the change can reduce the stiffness in the control pressure chamber.
  • the rear-hydraulic-pressure control device comprises a pressure-increase linear valve provided between the control pressure chamber and a high pressure source
  • the pressure-increase linear valve is in an open state when the hydraulic pressure in the control pressure chamber is less than an opening and closing switching pressure in a state in which a current to be supplied to a coil of the pressure-increase linear valve is kept, and the opening and closing switching pressure is determined by the current to be supplied to the coil of the pressure-increase linear valve, and
  • control-pressure-chamber stiffness reducer comprises a pressure-increase linear valve controller configured to increase the opening and closing switching pressure such that the opening and closing switching pressure is greater in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • a pressure differential force acting on the pressure-increase linear valve is less in the case where the hydraulic pressure in the control pressure chamber is high than in the case where the hydraulic pressure in the control pressure chamber is low.
  • the pressure-increase linear valve is in the closed state when an elastic force of a spring is equal to or greater than the pressure differential force in a state in which no current is supplied to the coil.
  • the pressure-increase linear valve is switched to the open state to cause the control pressure chamber to communicate with the high pressure source.
  • the pressure-increase linear valve when a greater current is supplied to the coil, the open state of the pressure-increase linear valve is established even when the pressure differential is small (even when the hydraulic pressure in the control pressure chamber is high). Thus, the pressure-increase linear valve tends to be open.
  • the rear-hydraulic-pressure control device comprises a target: hydraulic pressure determiner configured to determine a target hydraulic pressure in the control pressure chamber based on a brake request, and
  • the pressure-increase linear valve controller comprises a target-hydraulic-pressure-change-based pressure-increase linear valve controller configured to increase a current to be supplied to a coil of the pressure-increase linear valve such that the current to be supplied to the coil of the pressure-increase linear valve is greater in a case where a tendency of the target hydraulic pressure in the control pressure chamber which is determined by the target hydraulic pressure determiner is an increasing tendency than in a case where the tendency of the target hydraulic pressure in the control pressure chamber which is determined by the target hydraulic pressure determiner is a decreasing tendency.
  • the control pressure chamber is more easily caused to communicate with the high pressure source (the opening and closing switching pressure is higher) in the case where the target hydraulic pressure has the increasing tendency than in the case where the target hydraulic pressure has the decreasing tendency. As a result, the hydraulic pressure in the control pressure chamber can be well increased and brought closer to the target hydraulic pressure.
  • the rear-hydraulic-pressure control device comprises a pressure-increase and pressure-reduction controller configured to compare an actual hydraulic pressure and a target hydraulic pressure in the control pressure chamber with each other to at least execute one of pressure-increase control for increasing the hydraulic pressure in the control pressure chamber and pressure-reduction control for reducing the hydraulic pressure in the control pressure chamber, and
  • the pressure-increase linear valve controller is configured to increase the current to be supplied to the coil of the pressure-increase linear valve such that the current to be supplied to the coil of the pressure-increase linear valve is greater in a case where the pressure-increase control is to be executed by the pressure-increase and pressure-reduction controller than in a case where the pressure-reduction control is to be executed by the pressure-increase and pressure-reduction controller.
  • the rear-hydraulic-pressure control device comprises (a) a pressure-increase linear valve provided between the control pressure chamber and a high pressure source and (b) a target-hydraulic-pressure-based pressure-increase linear valve controller configured to control the pressure-increase linear valve such that the actual hydraulic pressure in the control pressure chamber is brought closer to a target hydraulic pressure, and
  • stiffness reducer comprises a pressure-increase-linear-valve-control target hydraulic pressure determiner configured to determine the target hydraulic pressure such that the target hydraulic pressure is greater in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • the pressure-increase linear valve in the open state when the actual hydraulic pressure in the control pressure chamber is less than the target hydraulic pressure, and the pressure-increase linear valve is switched to the closed state when the actual hydraulic pressure reaches the target hydraulic pressure, the pressure-increase linear valve tends to be open when the target hydraulic pressure is set to a large value.
  • the rear-hydraulic-pressure control device comprises (a) a pressure-increase linear valve provided between the control pressure chamber and a high pressure source, (b) a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source, and (c) an opening controller configured to establish open states of both of the pressure-increase linear valve and the pressure-reduction linear valve in at least a portion of a period in which the slip control device is in the operating state.
  • Both of the pressure-increase linear valve and the pressure-reduction linear valve at least need to be open in at least a portion of the period in which the slip control device is in the operating state and do not necessarily need to be open within the entire period in which the slip control device is in the operating state.
  • the rear-hydraulic-pressure control device comprises (a) a pressure-increase linear valve provided between the control pressure chamber and a high pressure source, (b) a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source, and (c) an opening controller configured to establish open states of both of the pressure-increase linear valve and the pressure-reduction linear valve when the hydraulic pressure in the control pressure chamber is within a set range determined by a target hydraulic pressure.
  • the pressure-increase linear valve and the pressure-reduction linear valve are closed in most cases.
  • both of the pressure-increase linear valve and the pressure-reduction linear valve are opened.
  • the control pressure chamber communicates with the high pressure source and the low pressure source respectively via the pressure-increase linear valve and the pressure-reduction linear valve (via restrictors), allowing working fluid to flow into and from the control pressure chamber.
  • a change in volume of the control pressure chamber i.e., increase and decrease in volume of the control pressure chamber) is allowed so as to allow vibrations of the hydraulic pressure.
  • the slip control device comprises a slip controller configured to use a hydraulic pressure in the hydraulic-pressure producing device to control a hydraulic pressure in each of the plurality of brake cylinders such that a slip of each of the plurality of wheels provided respectively for the plurality of brake cylinders is kept within an appropriate range determined by a coefficient of friction of a road surface.
  • examples of the slip controller include not only an anti-lock controller but also a traction controller and a vehicle stability controller.
  • each brake cylinder is in some cases controlled in a state in which the brake cylinder and the hydraulic-pressure producing device communicate with each other.
  • the slip control device comprises a plurality of slip-control electromagnetic valves capable of respectively controlling hydraulic pressures in the plurality of brake cylinders by respectively causing the plurality of brake cylinders to communicate with one of the hydraulic-pressure producing device and a low pressure source.
  • the low pressure source may be a master reservoir or a pressure reduction reservoir, for example.
  • the slip control device may be of a discharge type or a re-circulation type, for example.
  • the operating state of the slip control device is a state in which at least the slip-control electromagnetic valve is being operated. Opening and closing of the slip-control electromagnetic valve cause vibrations of a hydraulic pressure in an upstream side of the slip-control electromagnetic valve, and these vibrations are suppressed.
  • the slip-control electromagnetic valve include: a pressure increase valve (a pressure holding valve) provided between the hydraulic-pressure producing device and the brake cylinder; and a pressure reduction valve provided between the brake cylinder and the low pressure source.
  • the operating state of the slip control device is at least one of a state in which the slip-control electromagnetic valve is being operated and a state in which the pump device is being operated.
  • Operations of the pump device cause vibrations of a hydraulic pressure in an upstream side of the slip-control electromagnetic valve, and these vibrations are suppressed.
  • a damper is in most cases provided to suppress the vibrations caused by the operations of the pump device.
  • the hydraulic-pressure producing device is controlled to suppress the vibrations of the hydraulic pressure in the upstream portion. This eliminates a need for providing a damper, avoiding increase in size of the hydraulic braking system, resulting in reduced increase in cost.
  • the slip control device may be configured to include: a slip-control electromagnetic valve; a pressure reduction reservoir storing working fluid having flowed from the plurality of brake cylinders; and a pump device configured to pump up the working fluid out of the pressure reduction reservoir to supply the working fluid to the upstream portion.
  • each of at least one first slip-control electromagnetic valve as one or more of the plurality of slip-control electromagnetic valves is provided between the hydraulic-pressure producing device and a corresponding one of the plurality of brake cylinders, and
  • the slip control device comprises a pressure differential controller configured to control the at least one first slip-control electromagnetic valve such that a difference between an output hydraulic pressure of the hydraulic-pressure producing device and a hydraulic pressure in each of one or more of the plurality of brake cylinders to which the at least one first slip-control electromagnetic valve is connected is brought closer to a corresponding target pressure differential.
  • the respective hydraulic pressures in the plurality of brake cylinders are controllable by a plurality of slip-control electromagnetic valves, individually.
  • the rear-hydraulic-pressure control device comprises (a) at least one of a rearward chamber pressure-increase linear valve provided between the rearward chamber and a high pressure source and a rearward chamber pressure-reduction linear valve provided between the rearward chamber and a low pressure source and (b) a rearward chamber-hydraulic-pressure direct controller configured to control the at least one of the rearward chamber pressure-increase linear valve and the rearward chamber pressure-reduction linear valve to control the hydraulic pressure in the rearward chamber to control a hydraulic pressure in the front pressure chamber, and
  • the rearward chamber stiffness reducer comprises a direct rearward chamber stiffness reducer configured to control one or more of the at least one of the rearward chamber pressure-increase linear valve and the rearward chamber pressure-reduction linear valve to reduce the stiffness in the rearward chamber such that the stiffness in the rearward chamber is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state, and the direct rearward chamber stiffness reducer is comprised in the rearward chamber-hydraulic-pressure direct controller.
  • the pressure-increase linear valve and the pressure-reduction linear valve are directly connected to the rearward chamber, and the hydraulic pressure in the rearward chamber is controlled to control the hydraulic pressure in the front pressure chamber.
  • the hydraulic-pressure producing device may or may not include a manual hydraulic pressure source such as a master cylinder as described above.
  • the hydraulic pressure in the power hydraulic pressure source is used to control the hydraulic pressure in the upstream portion in a state in which the upstream portion is isolated from the manual hydraulic pressure source.
  • the upstream-portion hydraulic pressure controller suppresses the vibrations of the hydraulic pressure in the upstream portion.
  • the upstream-portion hydraulic pressure controller may be configured to include one or more electromagnetic valves and control the one or more electromagnetic valves to control the hydraulic pressure in the upstream portion and may be configured to control a pump motor of a pump device of the power hydraulic pressure source to control the hydraulic pressure in the upstream portion.
  • the hydraulic-pressure producing device comprises; (i) a high pressure source and (ii) at least one of an upstream pressure-increase linear valve provided between a high pressure source and the upstream portion and an upstream pressure-reduction linear valve provided between the upstream portion and a low pressure source, and
  • stiffness reducer is configured to control one or more of the at least one of the upstream pressure-increase linear valve and the upstream pressure-reduction linear valve to reduce the stiffness in the upstream portion such that the stiffness in the upstream portion is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.
  • the technical feature according to any one of the above forms (5) through (16) can be employed for control of the upstream pressure-increase linear valve and the upstream pressure-reduction linear valve.
  • a hydraulic braking system comprising;
  • a hydraulic-pressure producing device comprising (a) a pressurizing piston fluid-tightly and slidably fitted in a housing, (b) an advancing-force control device configured to apply an advance force from a position behind the pressurizing piston, the advance force being a force in an advance direction, and (c) a front pressure chamber provided in front of the pressurizing piston, the plurality of brake cylinders being connected to the front pressure chamber, the hydraulic-pressure producing device being capable of controlling a hydraulic pressure in the front pressure chamber using the advancing-force control device; and
  • a slip control device capable of individually controlling respective hydraulic pressures in the plurality of brake cylinders by causing each of the plurality of brake cylinders to communicate with any one of the front pressure chamber and a low pressure source
  • the advancing-force control device comprises a vibration suppressor configured to suppress a vibration of the hydraulic pressure in the front pressure chamber in a case where the slip control device is in an operating state.
  • the advancing-force control device may be configured to include (i) an electric motor and (ii) a motion converter.
  • the motion converter is also a motion transmission mechanism configured to convert a rotational power of an output shaft of the electric motor to an advance force to transmit the advance force to the pressurizing piston.
  • a hydraulic braking system comprising;
  • a hydraulic-pressure producing device comprising (i) a master cylinder comprising (a) a pressurizing piston fluid-tightly and slidably fitted in a housing, (b) a front pressure chamber provided in front of the pressurizing piston, the plurality of brake cylinders being connected to the front pressure chamber, and (c) a rearward chamber provided at a rear of the pressurizing piston, and (ii) a rear-hydraulic-pressure control device capable of controlling a hydraulic pressure in the rearward chamber; and
  • a slip control device capable of individually controlling respective hydraulic pressures in the plurality of brake cylinders by causing each of the plurality of brake cylinders to communicate with any one of the front pressure chamber and a low pressure source
  • the rear-hydraulic-pressure control device comprises a vibration suppressor configured to suppress a vibration of the hydraulic pressure in the front pressure chamber in a case where the slip control device is in an operating state.
  • a hydraulic braking system comprising;
  • a slip control device provided between the hydraulic-pressure producing device and the plurality of brake cylinders and comprising a pump device configured to transfer working fluid having flowed from the plurality of brake cylinders, back to an upstream portion located upstream of the plurality of brake cylinders,
  • the hydraulic-pressure producing device comprises a vibration suppressor configured to execute electronic control to suppress a vibration of a hydraulic pressure in the upstream portion.
  • a hydraulic braking system comprising:
  • a slip control device provided between the hydraulic-pressure producing device and the plurality of brake cylinders and configured to control a hydraulic pressure in each of at least one of the plurality of brake cylinders, the slip control device comprising a pump device configured to transfer working fluid having flowed from the plurality of brake cylinders, back to an upstream portion located upstream of the plurality of brake cylinders,
  • the hydraulic-pressure producing device comprises a stiffness reducer configured to reduce a stiffness in the upstream portion such that the stiffness in the upstream portion is less in a case where the pump device is in an operating state than in a case where the pump device is in a non-operating state.
  • FIG. 1 is a circuit diagram illustrating a hydraulic braking system according to a first embodiment of the present invention.
  • FIG. 2( a ) is a cross-sectional view illustrating a pressure-increase linear valve of the hydraulic braking system
  • FIG. 2( b ) is a view illustrating a characteristic of the pressure-increase linear valve.
  • FIG. 3( a ) is a cross-sectional view illustrating a pressure-reduction linear valve of the hydraulic braking system
  • FIG. 3( b ) is a view illustrating a characteristic of the pressure-reduction linear valve.
  • FIG. 4 is a view illustrating a brake ECU of the hydraulic braking system and devices connected to the brake ECU.
  • FIG. 5 is a view illustrating modes of control of currents to be supplied to coils of the pressure-increase linear valve and the pressure-reduction linear valve in the hydraulic braking system.
  • FIG. 6( a ) is a view conceptually illustrating an amount of opening of each of the pressure-increase linear valve and the pressure-reduction linear valve in anti-lock control.
  • FIG. 6( b ) is a view conceptually illustrating an amount of opening of each of the pressure-increase linear valve and the pressure-reduction linear valve in normal braking.
  • FIG. 7 is a flow chart illustrating a slip control program stored in a storage device of the brake ECU.
  • FIG. 8 is a flow chart illustrating a linear-valve control program stored in the storage device of the brake ECU.
  • FIG. 9 is a view illustrating a relationship between a hydraulic pressure in a front pressure chamber and a hydraulic pressure in a hydraulic brake cylinder for explaining problems to be solved by the present invention.
  • FIG. 10 is a circuit diagram of a hydraulic braking system according to a second embodiment of the present invention.
  • FIG. 11 is a circuit diagram of a hydraulic braking system according to a third embodiment of the present invention.
  • FIG. 12 is a view for explaining control of the pressure-reduction linear valve of the hydraulic braking system according to the above-described embodiment and for explaining a relationship between a pressure differential and a valve opening current with comparison between a normally open valve and a normally closed valve.
  • FIG. 13 is a circuit diagram of a hydraulic braking system according to a fourth embodiment of the present invention.
  • FIG. 14 is a circuit diagram of a hydraulic braking system according to a fifth embodiment of the present invention.
  • the present hydraulic braking system may be installed in hybrid vehicles, electric vehicles, fuel-cell vehicles, and internal combustion vehicles.
  • a regenerative braking force is applied to drive wheels, and regenerative cooperative control is executed.
  • the regenerative cooperative control is not executed in the internal combustion vehicle.
  • a braking force of a hydraulic brake is electrically controlled to have a desired magnitude.
  • the hydraulic brake system includes (i) brake cylinders 6 FL, 6 FR of hydraulic brakes 4 FL, 4 FR respectively provided for front left and right wheels 2 FL, 2 FR, and brake cylinders 12 RL, 12 RR of hydraulic brakes 10 RL, 10 RR respectively provided for rear left and right wheels 8 RL, 8 RR, (ii) a hydraulic-pressure producing device 14 capable of supplying a hydraulic pressure to these brake cylinders 6 FL, 6 FR, 12 RL, 12 RR, and (iii) a slip control device 16 provided between the hydraulic-pressure producing device 14 and the brake cylinders 6 FL, 6 FR, 12 RL, 12 RR.
  • Devices such as the hydraulic-pressure producing device 14 and the slip control device 16 are controlled by a brake ECU 20 (see FIG. 4 ) constituted mainly by a computer.
  • the hydraulic-pressure producing device 14 includes (i) a brake pedal 24 as a brake operating member, (ii) a master cylinder 26 , (iii) a rear-hydraulic-pressure control device 28 configured to control a hydraulic pressure in a rearward chamber of the master cylinder 26 .
  • the master cylinder 26 includes (a) a housing 30 and (b) pressurizing pistons 32 , 34 and an input piston 36 arranged in series and fluid-tightly and slidably fitted in a cylinder bore formed in the housing 30 .
  • Front pressure chambers 40 , 42 are defined in front of the respective pressurizing pistons 32 , 34 .
  • the brake cylinders 6 FL, 6 FR of the hydraulic brakes 4 FL, 4 FR provided for the respective front left and right wheels 2 FL, 2 FR are connected to the front pressure chamber 40 by a fluid passage 44
  • the brake cylinders 12 RL, 12 RR of the hydraulic brakes 10 RL, 10 RR provided for the respective rear left and right wheels 8 RL, 8 RR are connected to the front pressure chamber 42 by a fluid passage 46 .
  • each of the brake cylinders 6 FL, 6 FR, 12 RL, 12 RR actuates a corresponding one of the hydraulic brakes 4 FL, 4 FR, 10 RL, 10 RR to restrain rotation of a corresponding one of the wheels 2 FL, 2 FR, 8 RL, 8 RR.
  • each of devices such as the hydraulic brakes and electromagnetic valves which will be described below may be referred without suffixes (FL, FR, RL, RR) indicative of the corresponding wheels.
  • Return springs are respectively provided between the pressurizing piston 32 and the housing 30 and between the two pressurizing pistons 32 , 34 to urge the pressurizing pistons 32 , 34 backward or in a retracting direction.
  • the front pressure chambers 40 , 42 are in communication with a master reservoir (which may be referred to as “reservoir tank”) 52 .
  • the pressurizing piston 34 includes (a) a front piston portion 56 provided in a front portion thereof, (b) an intermediate piston portion 58 provided in an intermediate portion of the pressurizing piston 34 so as to protrude in its radial direction, and (c) a rear small-diameter portion 60 provided in a rear portion of the pressurizing piston 34 and having a diameter smaller than that of the intermediate piston portion 58 .
  • the front piston portion 56 and the intermediate piston portion 58 are fluid-tightly and slidably fitted in the housing 30 .
  • a space in front of the front piston portion 56 is the front pressure chamber 42
  • a space in front of the intermediate piston portion 58 is an annular chamber 62 .
  • the housing 30 is provided with an annular inner-circumferential-side protruding portion 64 , and the rear portion of the intermediate piston portion 58 , i.e., the rear small-diameter portion 60 is fluid-tightly and slidably fitted in the inner-circumferential-side protruding portion 64 .
  • a rearward chamber 66 is formed at a rear of the intermediate piston portion 58 and between the intermediate piston portion 58 and the inner-circumferential-side protruding portion 64 .
  • the input piston 36 is located at a rear of the pressurizing piston 34 , and an input chamber 70 is defined between the rear small-diameter portion 60 and the input piston 36 .
  • the brake pedal 24 is engaged with a rear portion of the input piston 36 by an operating rod 72 and other components.
  • the front piston portion 56 and the intermediate piston portion 58 of the pressurizing piston 34 constitute a pressurizing piston (or a pressurizing piston portion).
  • the annular chamber 62 and the input chamber 70 are connected to each other by a connecting passage 80 .
  • a communication control valve 82 is provided in the connecting passage 80 .
  • the communication control valve 82 is an electromagnetic open/close valve which is opened and closed according to a state of current supplied to a coil 82 s , specifically, the communication valve 82 is a normally closed valve which establishes its closed state when no current is supplied to the coil 82 s .
  • a portion of the connecting passage 80 which is located on one of opposite sides of the communication control valve 82 which is nearer to the annular chamber 62 is connected to the master reservoir 52 by a reservoir passage 84 in which a reservoir cut-off valve 86 is provided.
  • the reservoir cut-off valve 86 is an electromagnetic open/close valve which is opened and closed according to a state of current supplied to a coil 86 s , specifically, the reservoir cut-off valve 86 is a normally open valve which establishes its open state when no current is supplied to the coil 86 s.
  • a stroke simulator 90 is connected, by a simulator passage 88 , to the portion of the connecting passage 80 which is located on one of opposite sides of the communication control valve 82 which is nearer to the annular chamber 62 . Since the stroke simulator 90 is connected to the input chamber 70 by the simulator passage 88 and the connecting passage 80 , operations of the stroke simulator 90 are allowed when the communication control valve 82 is in its open state and are inhibited when the communication control valve 82 is in its closed state.
  • a hydraulic sensor 92 is provided in a portion of the connecting passage 80 which is located on one of opposite sides of the portion thereof to which the reservoir passage 84 is connected, and the one of opposite sides is nearer to the annular chamber 62 .
  • the hydraulic sensor 92 detects hydraulic pressures in the annular chamber 62 and the input chamber 70 in a state in which the annular chamber 62 and the input chamber 70 are in communication with each other and isolated from the master reservoir 52 .
  • the hydraulic pressures detected by the hydraulic sensor 92 have a magnitude related to an operating force of the brake pedal 24 . Accordingly, the hydraulic sensor 92 can be referred to as “operating-force sensor” and “operation-related hydraulic sensor”.
  • the rear-hydraulic-pressure control device 28 is connected to the rearward chamber 66 .
  • the rear-hydraulic-pressure control device 28 includes (a) a high pressure source 100 , (b) a regulator 102 , and (c) a linear valve device 103 .
  • the high pressure source 100 includes: a pump device 106 including a pump 104 and a pump motor 105 ; and an accumulator 108 configured to accumulate working fluid discharged from the pump device 106 in a pressurized state.
  • a hydraulic pressure of the working fluid accumulated in the accumulator 108 is called an accumulator pressure which is detected by an accumulator pressure sensor 109 .
  • the pump motor 105 is controlled so as to keep the accumulator pressure within a predetermined range.
  • the regulator 102 includes (d) a housing 110 , and (e) a pilot piston 112 and a control piston 114 provided in the housing 110 so as to be arranged in series in a direction parallel to an axis L.
  • the housing 110 has a stepped cylinder bore which includes: a large diameter portion in which the pilot piston 112 and the control piston 114 are fluid-tightly and slidably fitted; and a small diameter portion having a high pressure chamber 116 connected to the high pressure source 100 .
  • a space between the pilot piston 112 and the housing 110 is a pilot pressure chamber 120
  • a space at a rear of the control piston 114 is a control pressure chamber 122
  • a space between the control piston 114 and a step between the large diameter portion and the small diameter portion of the cylinder bore is a servo chamber 124 .
  • a high-pressure supply valve 126 is provided between the servo chamber 124 and the high pressure chamber 116 .
  • the high-pressure supply valve 126 is a normally closed valve and includes (f) a valve seat 130 , (g) a valve member 132 which can be seated on and moved off the valve seat 130 , and (h) a spring 136 for applying an elastic force to the valve member 132 in a direction in which the valve seat 130 is to be seated (i.e., a retracting direction).
  • a central portion of a main body of the control piston 114 has: a mating hole extending parallel to the axis L; and a fluid passage 140 having a portion extending in a direction perpendicular to the axis L (i.e., a radial direction) and communicating with the mating hole.
  • the fluid passage 140 is always in communication with a low pressure port connected to the master reservoir 52 .
  • a valve opening member 144 extending parallel to the axis L is fitted in the mating hole.
  • the valve opening member 144 has: a central portion in which is formed an axial direction passage 146 extending parallel to the axis L; a rear end portion which opens to the fluid passage 140 ; and a front end portion which is opposed to the valve member 132 .
  • the low pressure port and the front end portion of the valve opening member 144 which is opposed to the valve member 132 are connected to each other by the axial direction passage 146 and the fluid passage 140 .
  • a spring 150 is provided between the valve opening member 144 and the housing 110 to urge the control piston 114 (having the valve opening member 144 ) in its retracting direction.
  • pilot pressure chamber 120 is connected to the fluid passage 46 by a pilot passage 152 .
  • a hydraulic pressure in the pressure chamber 42 of the master cylinder 26 acts on the pilot piston 112 .
  • the rearward chamber 66 of the master cylinder 26 is connected to the servo chamber 124 by a servo passage 154 . Since the servo chamber 124 and the rearward chamber 66 are directly connected to each other, a hydraulic pressure in the servo chamber 124 and a hydraulic pressure in the rearward chamber 66 are principally equal to each other. It is noted that a servo-hydraulic-pressure sensor (which may be referred to as “rearward chamber hydraulic sensor”) 156 is provided in the servo passage 154 to detect the hydraulic pressure in the servo chamber 124 (i.e., the hydraulic pressure in the rearward chamber 66 ).
  • the linear valve device 103 including a pressure-increase linear valve 160 and a pressure-reduction linear valve 162 is connected to the control pressure chamber 122 .
  • a hydraulic pressure in the control pressure chamber 122 is controlled by control of currents supplied to a coil 160 s of the pressure-increase linear valve 160 and a coil 162 s of the pressure-reduction linear valve 162 .
  • the pressure-increase linear valve 160 includes a poppet valve 170 and a solenoid 172 .
  • the poppet valve 170 includes a valve seat 174 , a valve member 176 , and a spring 178 configured to apply an elastic force Fs to the valve member 176 in a direction in which the valve member 176 is moved toward the valve seat 174 .
  • the solenoid 172 includes the coil 160 s and a plunger 182 . When a current is supplied to the coil 160 s , an electromagnetic driving force Fd is generated. The plunger 182 applies this electromagnetic driving force Fd to the valve member 176 .
  • the pressure-increase linear valve 160 is provided in such a position that a pressure differential force Fp, which is related to a hydraulic pressure difference between the high pressure source 100 and the control pressure chamber 122 , acts on the valve member 176 in a direction in which the valve member 176 is moved away from the valve seat 174 .
  • Fp+Fd:Fs a pressure differential force
  • the pressure-increase linear valve 160 has a characteristic indicating a relationship illustrated in FIG. 2( b ) between a valve opening current IopenA and the pressure differential.
  • FIG. 2( b ) indicates that the poppet valve 170 is opened more easily in the case where an amount of the current supplied to the coil 160 s is large than in the case where an amount of the current supplied to the coil 160 s is small, even when the pressure differential force Fp is small. That is, the poppet valve 170 is open when the hydraulic pressure in the control pressure chamber 122 is lower than the hydraulic pressure in the control pressure chamber 122 which corresponds to the pressure differential determined by the supply current and the characteristic illustrated in FIG. 2( b ) . It is noted that the hydraulic pressure in the control pressure chamber 122 may be referred to as “opening and closing switching pressure”. The opening and closing switching pressure is larger in the case where the amount of the supply current is large than in the case where the amount of the supply current is small.
  • the pressure-reduction linear valve 162 includes a poppet valve 186 and a solenoid 188 .
  • the poppet valve 186 includes a valve seat 190 , a valve member 191 , and a spring 192 configured to apply an elastic force Fs in a direction in which the valve member 191 is moved away from the valve seat 190 .
  • the solenoid 188 includes the coil 162 s and a plunger 195 . When a current is supplied to the coil 162 s , an electromagnetic driving force Fd acts on the valve member 191 in a direction in which the valve member 191 is seated on the valve seat 190 .
  • a pressure differential force Fp which is related to a pressure differential between the control pressure chamber 122 and the master reservoir, acts on the valve member 191 in a direction in which the valve member 191 is moved away from the valve seat 190 .
  • the pressure-reduction linear valve 162 has a characteristic indicating a relationship illustrated in FIG. 3( b ) between a valve opening current IopenR and the pressure differential.
  • the poppet valve 186 is opened more easily in the case where an amount of the current supplied to the coil 162 s is large than in the case where an amount of the current supplied to the coil 162 s is small, even when the pressure differential (i.e., the hydraulic pressure in the control pressure chamber 122 ) is large. That is, the poppet valve 186 is open when the hydraulic pressure in the control pressure chamber 122 is higher than the pressure differential determined by the amount of current supplied to the coil 162 s and the characteristic illustrated in FIG. 3( b ) . It is noted that this pressure differential is equal to the hydraulic pressure in the control pressure chamber 122 and may be referred to as “opening and closing switching pressure”. The opening and closing switching pressure is lower in the case where the amount of the supply current is small than in the case where the amount of the supply current is large.
  • the slip control device 16 includes: pressure holding valves 200 FR, FL provided respectively between the pressure chamber 40 and the brake cylinder 6 FR and between the pressure chamber 40 and the brake cylinder 6 FL; pressure reduction valves 204 FR, FL provided respectively between the brake cylinder 6 FR and a pressure reduction reservoir 202 F and between the brake cylinder 6 FL and the pressure reduction reservoir 202 F; a pump device 206 F configured to pump up working fluid out of the pressure reduction reservoir 202 F to transfer the working fluid to areas located upstream of the respective pressure holding valves 200 FR, FL; pressure holding valves 200 RR, RL provided respectively between the pressure chamber 42 and the brake cylinder 12 RR and between the pressure chamber 42 and the brake cylinder 12 RL; pressure reduction valves 204 RR, RL provided respectively between the brake cylinder 12 RR and a pressure reduction reservoir 202 R and between the brake cylinder 12 RL and the pressure reduction reservoir 202 R; and a pump device 206 R configured to pump up working fluid out of the pressure reduction reservoir 202 R to transfer the working fluid to areas
  • Each of the pressure holding valve 200 and the pressure reduction valve 204 is an electromagnetic valve which is opened and closed by control of a current supplied to a corresponding one of coils 200 s , 204 s .
  • the pressure holding valve 200 is a normally open valve
  • the pressure reduction valve 204 is a normally closed valve.
  • Duty control is executed for the currents supplied to the coils 200 s , 204 s of the pressure holding valve 200 and the pressure reduction valve 204 , resulting in generation of a pressure differential having a magnitude determined by a duty ratio.
  • the duty ratio is determined such that an actual pressure differential which is obtained by subtracting a hydraulic pressure in a corresponding one of the brake cylinders 6 , 12 from a hydraulic pressure in a corresponding one of the front pressure chambers 40 , 42 is brought closer to a target pressure differential which is a difference between an estimated hydraulic pressure in the corresponding one of the front pressure chambers 40 , 42 and a target hydraulic pressure in the corresponding one of the brake cylinders 6 , 12 .
  • the pressure differential is larger, and the hydraulic pressure in the corresponding one of the brake cylinders 6 , 12 is lower with respect to the hydraulic pressure in the corresponding one of the front pressure chambers 40 , 42 in the case where the duty ratio is large than in the case where the duty ratio is small.
  • duty control is executed based on a duty ratio determined such that an actual hydraulic pressure in the corresponding one of the brake cylinders 6 , 12 which is obtained by subtracting a hydraulic pressure in a corresponding one of the pressure reduction reservoirs 202 F, R (which can be estimated to an atmospheric pressure) from the hydraulic pressure in the corresponding one of the brake cylinders 6 , 12 is brought closer to the target hydraulic pressure.
  • the hydraulic pressures in the respective brake cylinders 6 , 12 are smaller in the case where the duty ratio is large than in the case where the duty ratio is small.
  • the pump devices 206 F, R are operated to pump up the working fluid out of the respective pressure reduction reservoirs 202 F, R and transfer the working fluid to respective supply portions 212 F, R located upstream of the pressure holding valve 200 .
  • the present slip control device is of a re-circulation type.
  • the supply portions 212 F, R are portions of the respective fluid passages 44 , 46 and are in communication with the respective front pressure chambers 40 , 42 .
  • the fluid passages 44 , 46 respectively include upstream portions 214 F, R which include the respective connecting portions 212 F, R and portions of the respective fluid passages 44 , 46 which are located upstream of the pressure holding valve 200 .
  • the brake ECU 20 is mainly constituted by a computer including an executing device 220 , a storage device 222 , and an input/output device 224 .
  • Devices connected to the input/output device 224 include: the above-described operating hydraulic sensor 92 ; the accumulator pressure sensor 109 ; the servo-hydraulic-pressure sensor 156 ; a stroke sensor 230 configured to detect a stroke of the brake pedal 24 (hereinafter may be referred to as “operating stroke”); a wheel speed sensor 232 configured to detect a speed of each of the front left and right and rear left and right wheels 2 FL, FR, 8 RL, RR; a yaw rate sensor 234 configured to detect a yaw rate of the vehicle; the pump motors 105 , 210 which are connected to the input/output device 224 via a drive circuit, not shown; and the coils of the electromagnetic valves such as the pressure-increase linear valve 160 , the pressure-reduction
  • the storage device 222 of the brake ECU 20 stores a plurality of programs and tables, for example.
  • the regenerative cooperative control is principally executed in the case where the present hydraulic braking system is installed in a vehicle such as the electric vehicles and the hybrid vehicles.
  • a brake request is issued when the brake pedal 24 is depressed by a driver, for example.
  • the hydraulic brakes 4 , 10 are not actuated.
  • the communication control valve 82 is opened, and the reservoir cut-off valve 86 is closed, so that the input chamber 70 and the annular chamber 62 communicate with each other, are isolated from the master reservoir, and communicate with the stroke simulator 90 .
  • the area of a pressure receiving surface of the intermediate piston portion 58 which faces the annular chamber 62 is equal to that of the rear small-diameter portion 60 which faces the input chamber 70 .
  • the linear valve device 103 is not controlled, so that the regulator 102 is in its non-operating state.
  • no hydraulic pressure is supplied to the rearward chamber 66 of the master cylinder 26 .
  • the pressurizing piston 34 is not advanced, so that no hydraulic pressure is generated in the front pressure chambers 40 , 42 , and each of the hydraulic brakes 4 , 10 is in its non-operating state.
  • the linear valve device 103 is controlled to increase the hydraulic pressure in the control pressure chamber 122 .
  • the control piston 114 is advanced, resulting in increase in the hydraulic pressure in the servo chamber 124 .
  • the high-pressure supply valve 126 is switched to its open state and fluidically coupled with the high pressure chamber 116 , so that the hydraulic pressure in the servo chamber 124 is supplied to the rearward chamber 66 .
  • the hydraulic pressure in the rearward chamber 66 moves the pressurizing piston 34 forward, so that hydraulic pressures are generated in the front pressure chambers 40 , 42 and supplied to the respective brake cylinders 6 , 12 to actuate the respective hydraulic brakes 4 , 10 .
  • the hydraulic pressure in each of the brake cylinders 6 , 12 is controlled by the control of the linear valve device 103 such that the hydraulic braking force and the regenerative braking force are sufficient for the braking force requested by the driver (which may be referred to as “requested braking force” or “requested total braking force”).
  • Each of the pressure holding valve 200 and the pressure reduction valve 204 is located at its illustrated original position, and the pump motor 210 is in a rest state.
  • the linear valve device 103 is controlled such that the hydraulic brakes 4 , 10 generate a force enough for the braking force requested by the driver.
  • the requested braking force (i.e., the requested total braking force) is determined based on an operation state of the brake pedal 24 (which can be represented by at least one of the operating stroke detected by the stroke sensor 230 and the operating force detected by the operating hydraulic sensor 92 ).
  • a target hydraulic braking force is determined based on a value obtained by subtracting the regenerative braking force from the requested braking force.
  • the target hydraulic braking force is determined based on the requested braking force.
  • target hydraulic pressures in the respective front pressure chambers 40 , 42 are determined based on the target hydraulic braking force, and a target hydraulic pressure Pref in the rearward chamber 66 is determined based on these target hydraulic pressures, and a target hydraulic pressure in the control pressure chamber 122 is determined.
  • the amounts of currents supplied to the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are controlled such that an actual hydraulic pressure in the control pressure chamber 122 is brought closer to the target hydraulic pressure.
  • the hydraulic pressures in the respective front pressure chambers 40 , 42 and the hydraulic pressure in the rearward chamber 66 have a relationship which is determined by, e.g., construction of the master cylinder 26 .
  • a hydraulic pressure in the control pressure chamber 122 and the hydraulic pressure in the servo chamber 124 which is equal in magnitude to the hydraulic pressure in the rearward chamber 66 have a relationship which is determined by, e.g., construction of the regulator 102 .
  • the hydraulic pressure in the servo chamber 124 and the hydraulic pressure in the control pressure chamber 122 are made equal to each other.
  • the linear valve device 103 is controlled such that an actual hydraulic pressure in the rearward chamber 66 (which is detected by the servo-hydraulic-pressure sensor 156 and may be hereinafter referred to as “actual rearward chamber hydraulic pressure P*”) is brought closer to a target hydraulic pressure in the rearward chamber 66 which is determined based on the target hydraulic pressures in the respective front pressure chambers 40 , 42 .
  • This target hydraulic pressure in the rearward chamber 66 is equal in magnitude to a target hydraulic pressure in the servo chamber 124 and may be hereinafter referred to as “target rearward chamber hydraulic pressure Pref.”.
  • a control mode is determined based on at least one of a tendency of change in the target rearward chamber hydraulic pressure Pref and a difference between the target rearward chamber hydraulic pressure Pref and the actual rearward chamber hydraulic pressure P*.
  • a pressure increase mode is set in at least one of the case where the target rearward chamber hydraulic pressure Pref has an increasing tendency and the case where the actual rearward chamber hydraulic pressure P* is low with respect to the target rearward chamber hydraulic pressure Pref.
  • a pressure reduction mode is set in at least one of the case where the target rearward chamber hydraulic pressure Pref has a decreasing tendency and the case where the actual rearward chamber hydraulic pressure P* is high with respect to the target rearward chamber hydraulic pressure Pref.
  • a pressure holding mode is set in at least one of the case where the target rearward chamber hydraulic pressure Pref is substantially constant and the case where the actual rearward chamber hydraulic pressure P* falls within a set range which is determined by the target rearward chamber hydraulic pressure Pref.
  • control mode may be determined in any other methods.
  • the pressure-increase linear valve (SLA) 160 and the pressure-reduction linear valve (SLR) 162 are controlled so as to be in the open state and the closed state, respectively.
  • a current (Iopen+IFB) is supplied to the coil 160 s of the pressure-increase linear valve 160 , and the current (Iopen+IFB) is the sum of a valve opening current Iopen which is determined by the characteristic illustrated in FIG.
  • a current (which may be hereinafter referred to as “seal current Iseal”) enough to keep the pressure-reduction linear valve 162 in the closed state is supplied to the coil 162 s of the pressure-reduction linear valve 162 .
  • the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are controlled so as to be in the closed state and the open state, respectively.
  • No current is supplied to the coil 160 s of the pressure-increase linear valve 160 .
  • a current (Iopen+IFB) is supplied to the coil 162 s of the pressure-reduction linear valve 162 , and the current (Iopen+IFB) is the sum of: a valve opening current Iopen determined by the target rearward chamber hydraulic pressure Pref and the table in FIG. 3( b ) ; and a feedback current IFB ( ⁇ 0) determined based on a deviation between the actual rearward chamber hydraulic pressure P* and the target rearward chamber hydraulic pressure Pref.
  • each of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 is controlled so as to be in the closed state.
  • No current is supplied to the coil 160 s of the pressure-increase linear valve 160
  • the seal current Iseal is supplied to the coil 162 s of the pressure-reduction linear valve 162 .
  • FIG. 6( b ) conceptually illustrates states of controls for the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 .
  • the pressure-increase linear valve 160 is open within a period in which the actual rearward chamber hydraulic pressure P* is lower than the target rearward chamber hydraulic pressure Pref, and the pressure-increase linear valve 160 is closed when the actual rearward chamber hydraulic pressure P* has reached substantially the target rearward chamber hydraulic pressure Pref.
  • the pressure-reduction linear valve 162 is kept closed within a period in which the actual rearward chamber hydraulic pressure P* is lower than a magnitude (Pref+Px) obtained by adding a hydraulic pressure (Px) to the target rearward chamber hydraulic pressure Pref.
  • the pressure-reduction linear valve 162 is open within a period in which the actual rearward chamber hydraulic pressure P* is higher than the target rearward chamber hydraulic pressure Pref, and the pressure-reduction linear valve 162 is closed when the actual rearward chamber hydraulic pressure P* has reached substantially the target rearward chamber hydraulic pressure Pref.
  • the pressure-increase linear valve 160 is kept closed.
  • the current supplied to each of the respective coils 160 s , 162 s of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 is principally controlled such that a corresponding one of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 is closed when the actual rearward chamber hydraulic pressure P* is equal to substantially the target rearward chamber hydraulic pressure Pref.
  • both of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are not in the open state at the same time.
  • Anti-lock control is initiated when a braking force acting on each of the wheels 2 , 8 becomes excessively high with respect to a coefficient of friction of a road surface.
  • the slip control device 16 controls the hydraulic pressures in the respective brake cylinders 6 , 12 individually to restrain slipping of the wheels 2 , 8 under braking, so that each of the hydraulic pressures in the respective brake cylinders 6 , 12 is kept within an appropriate range determined by the coefficient of friction of the road surface.
  • each pressure holding valve 200 The current to be supplied to the coil of each pressure holding valve 200 is controlled such that the actual pressure differential is brought closer to the target pressure differential between the estimated hydraulic pressure in the corresponding one of the front pressure chambers 40 , 42 and the target hydraulic pressure in the corresponding one of the brake cylinders 6 , 12 .
  • the hydraulic pressures in the respective front pressure chambers 40 , 42 are estimated, as hydraulic pressures Pm, based on the target hydraulic pressures in the respective front pressure chambers 40 , 42 which are determined by the requested hydraulic braking force. Also, it is possible to consider that each of the hydraulic pressures in the respective brake cylinders 6 , 12 is equal to a corresponding one of the hydraulic pressures in the respective front pressure chambers 40 , 42 before the initiation of the anti-lock control.
  • the hydraulic pressures in the respective front pressure chambers 40 , 42 are estimated, as hydraulic pressures Pw, based on the estimated hydraulic pressure in the corresponding one of the front pressure chambers 40 , 42 just before the initiation of the anti-lock control and based on the control modes of the pressure holding valve 200 and the pressure reduction valve 204 .
  • a target hydraulic pressure Pwref in each of the brake cylinders 6 , 12 is obtained based on, e.g., a slipping state of a corresponding one of the wheels 2 , 8 .
  • an amount of the current to be supplied to the coil of each pressure holding valve 200 is determined such that the actual pressure differential (Pm ⁇ Pw) is brought closer to the target pressure differential (Pm ⁇ Pwref), and then a duty ratio for controlling the supply current is determined.
  • each pressure reduction valve 204 The current to be supplied to the coil of each pressure reduction valve 204 is controlled such that the estimated hydraulic pressure Pw in the corresponding one of the brake cylinders 6 , 12 is brought closer to the target hydraulic pressure Pwref. Each pressure reduction valve 204 is switched to the open state in the case where the corresponding one of the hydraulic pressures in the respective brake cylinders 6 , 12 is reduced.
  • the pump devices 206 F, R are operated to pump up the working fluid out of the respective pressure reduction reservoirs 202 F, R and transfer the working fluid back to the respective upstream portions 214 F, R (which are located upstream of the pressure holding valve 200 and the brake cylinders 6 , 12 ).
  • hydraulic pressures in the respective upstream portions 214 F, R vibrate due to operations of the slip control device 16 .
  • each of the hydraulic pressures in the respective brake cylinders 6 , 12 is reduced with respect to the corresponding one of the hydraulic pressures in the respective front pressure chambers 40 , 42 due to the operations of the pressure reduction valve 204 and the pressure holding valve 200 during the anti-lock control, resulting in generation of a hydraulic pressure difference between each of the brake cylinders 6 , 12 and the corresponding one of the front pressure chambers 40 , 42 .
  • the hydraulic pressure in the upstream portion 214 may be vibrated with opening and closing of the pressure holding valve 200 .
  • the hydraulic pressure in the upstream portion 214 may be vibrated by, e.g., pulsation due to the operations of the pumps 208 F, R.
  • the vibrations of the hydraulic pressure which are caused by the pulsation due to the operations of the pumps 208 F, R are vibrations with a frequency of greater than or equal to a set value.
  • the vibrations of the hydraulic pressures in the respective upstream portions 214 F, R i.e., the vibrations of the hydraulic pressures in the respective front pressure chambers 40 , 42 are transferred to the rearward chamber 66 via the pressurizing piston 34 and then transferred to the control pressure chamber 122 via the control piston 114 of the regulator 102 .
  • the current to be supplied to the linear valve device 103 is increased and reduced following the vibrations of the hydraulic pressure in the control pressure chamber 122 to suppress the vibrations.
  • it is difficult to suppress the vibrations by increasing and reducing the current to be supplied to the linear valve device 103 following the vibrations of the hydraulic pressures in the respective upstream portions 214 F, R.
  • the stiffness in the control pressure chamber 122 is reduced in the present embodiment.
  • a current (Iopen+ ⁇ ) is supplied to the coil 160 s of the pressure-increase linear valve 160
  • a current (Iopen ⁇ ) is supplied to the coil 162 s of the pressure-reduction linear valve 162 .
  • the current (Iopen+ ⁇ ) is a current obtained by adding a set current ⁇ to the valve opening current Iopen determined by the characteristic illustrated in FIG. 2( b ) and the pressure differential between the target rearward chamber hydraulic pressure Pref and the accumulator pressure.
  • the current (Iopen ⁇ ) is a current obtained by subtracting a set current ⁇ (>0) from the valve opening current Iopen determined by the target rearward chamber hydraulic pressure Pref and the characteristic illustrated in FIG. 3( b ) .
  • the above-described operations in the pressure increase mode are also performed in the case where the pressure holding mode is set.
  • a current (Iopen+ ⁇ ) obtained by adding a set current ⁇ to the valve opening current Iopen is supplied to the coil 160 s of the pressure-increase linear valve 160
  • a current (Iopen ⁇ ) obtained by subtracting a set current ⁇ (>0) from the valve opening current Iopen is supplied to the coil 162 s of the pressure-reduction linear valve 162 .
  • the set current ⁇ is greater than the set current ⁇ ( ⁇ > ⁇ )
  • the set current ⁇ is greater than the set current ⁇ ( ⁇ > ⁇ ).
  • FIG. 6( a ) conceptually illustrates states of controls for the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 .
  • the pressure-increase linear valve 160 is open within a period in which the actual rearward chamber hydraulic pressure P* is lower than a hydraulic pressure (Pref+P ⁇ ) obtained by adding a set pressure P ⁇ determined by, e.g., the set current ⁇ to the target rearward chamber hydraulic pressure Pref, and the pressure-increase linear valve 160 is closed when the actual rearward chamber hydraulic pressure P* has reached the hydraulic pressure (Pref+P ⁇ ).
  • a hydraulic pressure Pref+P ⁇
  • the pressure-reduction linear valve 162 is open within a period in which the actual rearward chamber hydraulic pressure P* is higher than a hydraulic pressure (Pref ⁇ P ⁇ ) obtained by subtracting a set pressure P determined by the set current ⁇ from the target rearward chamber hydraulic pressure Pref, and the pressure-reduction linear valve 162 is closed when the actual rearward chamber hydraulic pressure P* has reached the hydraulic pressure (Pref ⁇ P ⁇ ).
  • both of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are in the open state within a period in which the actual rearward chamber hydraulic pressure P* falls within a set range determined by the target hydraulic pressure Pref ⁇ (Pref ⁇ P ⁇ ) ⁇ P* ⁇ (Pref+P ⁇ ) ⁇ .
  • This state allows the working fluid to flow into and out of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 (via restrictors) in the control pressure chamber 122 , allowing change in volume of the control pressure chamber 122 (i.e., increase and reduction in volume of the control pressure chamber 122 ), resulting in reduced stiffness in the control pressure chamber 122 .
  • the vibrations of the hydraulic pressure in the control pressure chamber 122 are absorbed.
  • an amount of opening of the pressure-increase linear valve 160 is greater than an amount of opening of the pressure-reduction linear valve 162 in the case where the actual rearward chamber hydraulic pressure P* is substantially equal to the target rearward chamber hydraulic pressure Pref.
  • the hydraulic pressure ⁇ P*> at which the amount of opening of the pressure-increase linear valve 160 and that of the pressure-reduction linear valve 162 are equal to each other is greater than the target rearward chamber hydraulic pressure Pref.
  • the actual rearward chamber hydraulic pressure P* does not easily become lower than the target rearward chamber hydraulic pressure Pref.
  • the pressure-increase linear valve 160 is open within a period in which the actual rearward chamber hydraulic pressure P* is lower than a hydraulic pressure (Pref+P ⁇ ) obtained by adding a set pressure P ⁇ determined by, e.g., the set current ⁇ to the target rearward chamber hydraulic pressure Pref.
  • the pressure-reduction linear valve 162 is open within a period in which the actual rearward chamber hydraulic pressure P* is higher than a hydraulic pressure (Pref ⁇ P ⁇ ) obtained by subtracting a set pressure P ⁇ determined by, e.g., the set current ⁇ from the target rearward chamber hydraulic pressure Pref.
  • both of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are in the open state within a period in which the actual rearward chamber hydraulic pressure P* falls within a set range determined by the target rearward chamber hydraulic pressure Pref ⁇ (Pref ⁇ P ⁇ ) ⁇ P* ⁇ (Pref+P ⁇ ) ⁇ . Since the set current ⁇ is greater than the set current ⁇ , an amount of opening of the pressure-reduction linear valve 162 is greater than an amount of opening of the pressure-increase linear valve 160 .
  • the hydraulic pressure ⁇ P*> at which the amount of opening of the pressure-reduction linear valve 162 and that of the pressure-increase linear valve 160 are equal to each other is less than the target rearward chamber hydraulic pressure Pref. As a result, the actual rearward chamber hydraulic pressure P* does not easily become higher than the target rearward chamber hydraulic pressure Pref.
  • the slip control device 16 is controlled by execution of a slip control program illustrated in a flow chart in FIG. 7 .
  • Step S 1 it is determined whether the anti-lock control is being executed.
  • Step S 2 it is determined at S 2 whether initiating conditions are satisfied. For example, it is determined that the initiating conditions are satisfied in the case where the wheel is slipped excessively under braking. When the initiating conditions are not satisfied, the slip control device 16 is not controlled.
  • the anti-lock control is executed at S 3 .
  • an anti-lock control flag is set.
  • the currents to be supplied to the pressure holding valve 200 and the pressure reduction valve 204 are controlled as described above.
  • the pump motor 210 is activated to cause the pump 208 to pump up the working fluid out of the pressure reduction reservoir 202 and transfer the working fluid to the upstream portion 214 .
  • the anti-lock control it is determined at S 4 whether terminating conditions are satisfied. For example, it is determined that the terminating conditions are satisfied in the case where an operation for the brake pedal 24 is canceled or in the case where slipping of the wheel under braking is kept within an appropriate range. When the terminating conditions are not satisfied, a negative decision (NO) is made, and the processings at S 1 , S 4 , and S 3 are executed repeatedly to continue the anti-lock control. When the terminating conditions are satisfied, a processing for terminating the anti-lock control is executed at S 5 . The pump motor 210 is stopped, and the pressure holding valve 200 and the pressure reduction valve 204 are returned to their respective original positions.
  • the linear valve device 103 is controlled in accordance with execution of a linear-valve control program illustrated in a flow chart in FIG. 8 .
  • the target rearward chamber hydraulic pressure Pref is determined at S 9 based on a requested braking force.
  • the control mode is determined at S 10 based on elements including a tendency of change in the target rearward chamber hydraulic pressure Pref.
  • the control mode is any of the pressure increase mode, the pressure holding mode, and the pressure reduction mode.
  • the control mode is the pressure increase mode
  • a positive decision (YES) is made at S 15
  • the same processing as executed when the control mode is the pressure increase mode is executed at S 17 .
  • a positive decision YES
  • both of the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are switched to the open state, which allows change in volume of the control pressure chamber 122 , resulting in reduced stiffness.
  • the vibrations of the hydraulic pressure in the control pressure chamber 122 due to the operation of the slip control device 16 are well absorbed, making it possible to suppress the vibrations of the hydraulic pressures in the respective front pressure chambers 40 , 42 .
  • the currents to be supplied to the pressure-increase linear valve 160 and the pressure-reduction linear valve 162 are not increased or reduced with vibrations. Accordingly, it is possible to well absorb even vibrations with a large frequency such as vibrations caused by pulsation of the pump device 206 . This eliminates the need for providing a damper, avoiding increase in size of the hydraulic braking system, resulting in reduced increase in cost.
  • the amount of opening of the pressure-increase linear valve 160 is made greater than the amount of opening of the pressure-reduction linear valve 162
  • the amount of opening of the pressure-reduction linear valve 162 is made greater than the amount of opening of the pressure-increase linear valve 160 . Accordingly, the actual rearward chamber hydraulic pressure P* can be controlled to have a magnitude near that of the target rearward chamber hydraulic pressure Pref, thereby improving the control accuracy for the hydraulic pressure in the brake cylinder in the anti-lock control, which can well avoid a long braking distance.
  • portions of the brake ECU 20 which store and execute the processings at S 16 -S 18 in the linear-valve control program illustrated in the flow chart in FIG. 8 constitute a stiffness reducer, a rearward chamber stiffness reducer, a control-pressure-chamber stiffness reducer, a pressure-reduction linear valve controller, a pressure-increase linear valve controller, an opening controller, and a volume-change allowing portion, for example.
  • portions of the brake ECU 20 which store and execute the processing at S 16 constitute a target-hydraulic-pressure-change-based pressure-increase linear valve controller, for example.
  • Portions of the brake ECU 20 which store and execute the processing at S 18 constitute a target-hydraulic-pressure-change-based pressure-reduction linear valve controller, for example. Portions of the brake ECU 20 which store and execute the processings at S 12 -S 18 constitute a control-pressure-chamber hydraulic pressure controller, for example. Portions of the brake ECU 20 which store and execute the processing at S 9 constitute a target hydraulic pressure determiner, for example.
  • portions of the brake ECU 20 which store and execute the processing at S 3 in the slip control program illustrated in the flow chart in FIG. 7 constitute a slip controller, for example.
  • Each of the pressure holding valve 200 and the pressure reduction valve 204 constitutes a slip-control electromagnetic valve, for example.
  • the hydraulic braking system may be configured as illustrated in FIG. 10 .
  • the hydraulic pressure in the rearward chamber 66 is directly controlled by control for the pressure-increase linear valve and the pressure-reduction linear valve. It is noted that the same reference numerals as used in the first embodiment are used to designate the corresponding elements of this embodiment, and an explanation of which is dispensed with.
  • a rear-hydraulic-pressure control device 250 is connected to the rearward chamber 66 .
  • the rear-hydraulic-pressure control device 250 does not include the regulator but includes the high pressure source 100 and a linear valve device 252 .
  • the linear valve device 252 includes: a pressure-increase linear valve 254 as a rearward chamber pressure-increase linear valve provided between the high pressure source 100 and the rearward chamber 66 ; and a pressure-reduction linear valve 256 as a rearward chamber pressure-reduction linear valve provided between the rearward chamber 66 and the master reservoir 52 .
  • a rearward chamber hydraulic sensor 258 is provided for detecting the hydraulic pressure in the rearward chamber 66 .
  • currents to be supplied to a coil 254 s of the pressure-increase linear valve 254 and a coil 256 s of the pressure-reduction linear valve 256 are controlled as in the first embodiment.
  • the pressure-increase linear valve 254 and the pressure-reduction linear valve 256 are opened, allowing change in volume of the rearward chamber 66 , resulting in lower stiffness.
  • the vibrations of the hydraulic pressure are absorbed in the rearward chamber 66 , thereby well suppressing the vibrations of the hydraulic pressures in the respective front pressure chambers 40 , 42 , resulting in improved control accuracy for the hydraulic pressures in the respective brake cylinders 6 , 12 .
  • portions of the brake ECU 20 which store and execute the linear-valve control program constitute a rearward chamber hydraulic pressure controller.
  • portions of the brake ECU 20 which store and execute the processings at S 16 -S 18 in the linear-valve control program constitute a direct rearward chamber stiffness reducer, for example.
  • the construction of the master cylinder is not limited to the construction in the first and second embodiments.
  • the master cylinder may have any construction as long as the master cylinder includes the rearward chamber provided at a rear of the pressurizing piston.
  • the hydraulic braking system may be configured as illustrated in FIG. 11 . It is noted that the same reference numerals as used in the first and second embodiments are used to designate the corresponding elements of this embodiment, and an explanation of which is dispensed with.
  • a master cylinder 300 includes two pressurizing pistons 302 , 303 .
  • Front pressure chambers 304 , 305 are defined in front of the respective pressurizing pistons 302 , 303 .
  • the brake cylinders 6 for the front left and right wheels and the brake cylinders for the rear left and right wheels are connected to the respective front pressure chambers 304 , 305 via respective master passages 306 , 307 .
  • FIG. 11 illustrates brake lines for the front wheels but omits illustration of brake lines for the rear wheels.
  • a slip control device 310 is provided between the front pressure chamber 304 and the brake cylinders 6 FL, FR of the respective front left and right wheels 2 FL, FR. Since the configuration of the slip control device 310 is similar to a portion of the configuration of the slip control device 16 in the first embodiment, the same reference numerals as used in the first embodiment are used to designate the corresponding elements of this embodiment, and an explanation of which is dispensed with.
  • a stroke simulator device 312 At a portion of the master passage 306 between the upstream portion 214 F and the front pressure chamber 304 , a stroke simulator device 312 , a master cut-off valve 314 , and an upstream control device 316 are provided in this order from upstream side.
  • the master cut-off valve 314 is a normally-open electromagnetic open/close valve.
  • the stroke simulator device 312 includes a normally-closed simulator control valve and a stroke simulator.
  • the upstream control device 316 includes a power hydraulic pressure source 320 as a high pressure source and a linear valve device 322 .
  • the linear valve device 322 includes: a pressure-increase linear valve 324 as a normally-closed upstream pressure-increase linear valve provided between the high pressure source 320 and the upstream portion 214 F; and a pressure-reduction linear valve 328 as a normally-closed upstream pressure-reduction linear valve provided between the upstream portion 214 F and a reservoir 326 .
  • the hydraulic pressure in the upstream portion 214 F is detected by a hydraulic sensor 330 .
  • Components such as the slip control device 310 and the linear valve device 322 are controlled by, e.g., a brake ECU 340 mainly constituted by a computer.
  • the upstream portion 214 F is isolated from the front pressure chamber 304 , and the linear valve device 322 is controlled to control the hydraulic pressure in the upstream portion 214 F, thereby controlling the hydraulic pressures in the brake cylinders 6 for the respective front left and right wheels in common.
  • a target hydraulic pressure in the upstream portion 214 F is determined based on a requested braking force of the driver.
  • the linear valve device 322 is controlled such that an actual hydraulic pressure in the upstream portion 214 F which is detected by the hydraulic sensor 330 is brought closer to the target hydraulic pressure.
  • the slip control device 16 is in its non-operating state, the pump motor 210 is in the rest state.
  • the hydraulic pressures in the respective brake cylinders 6 FL, FR are controlled by the linear valve device 322 in common and are individually controlled by the slip control device 310 .
  • the hydraulic pressure in the upstream portion 214 F is controlled by the linear valve device 322 .
  • the pressure-increase linear valve 324 is controlled in the same manner as in the first embodiment. In the case where the pressure increase mode or the pressure holding mode is set, a current (Iopen+ ⁇ ′) is supplied to the pressure-increase linear valve 324 . In the case where the pressure reduction mode is set, a current (Iopen+ ⁇ ′) is supplied to the pressure-increase linear valve 324 . Since the pressure-reduction linear valve 328 is a normally closed valve, the pressure-reduction linear valve 328 has a construction similar to that of the pressure-increase linear valve 324 and has a characteristic similar to the characteristic illustrated in FIG. 2( b ) (see FIG. 12 ). As illustrated in FIG.
  • the supply current is increased, and the opening and closing switching pressure is reduced during the anti-lock control is being executed.
  • a current Iopen+ ⁇ ′
  • a current Iopen+ ⁇ ′
  • each of the pressure-increase linear valve 324 and the pressure-reduction linear valve 328 is open.
  • the vibrations of the hydraulic pressure in the upstream portion 214 F in the anti-lock control are suppressed, thereby improving the control accuracy for the hydraulic pressure in the brake cylinder, which can well avoid a long braking distance.
  • a portion of the brake ECU 340 which controls the pressure-increase linear valve 324 and the pressure-reduction linear valve 328 constitutes a stiffness reducer 342 , for example.
  • the upstream control device 316 includes the linear valve device 322 .
  • the power hydraulic pressure source 320 may be controlled to suppress the vibrations in the upstream portion 214 F.
  • the hydraulic braking system may be configured as illustrated in FIG. 13 . It is noted that the same reference numerals as used in the first through third embodiments are used to designate the corresponding elements of this embodiment, and an explanation of which is dispensed with.
  • the hydraulic braking system illustrated in FIG. 13 includes a slip control device 400 of a discharge type and does not include a pump device.
  • the brake cylinders 6 FL, FR, 12 RL, RR for the respective front left and right and rear left and right wheels 2 FL, FR, 8 RL, RR are connected to a common passage 410 respectively via individual pressure-increase passages 412 FL, FR, RL, RR.
  • the brake cylinders 6 FL, FR, 12 RL, RR and a master reservoir 414 are connected to each other via respective individual pressure-reduction passages 416 FL, FR, RL, RR.
  • Pressure holding valves 420 FL, FR, RL, RR are provided on the respective individual pressure-increase passages 412 FL, FR, RL, RR.
  • Pressure reduction valves 422 FL, FR, RL, RR are provided on the respective individual pressure-reduction passages 416 FL, FR, RL, RR.
  • a master cylinder 430 and a hydraulic booster 432 are connected to the common passage 410 via respective manual passages 434 , 436 .
  • a hydraulic-pressure producing device 438 is connected to the common passage 410 .
  • Manual cut-off valves 440 , 442 are provided on the respective manual passages 434 , 436 .
  • the hydraulic-pressure producing device 438 includes the power hydraulic pressure source 320 as the high pressure source and the linear valve device 322 .
  • the linear valve device 322 includes: a normally-closed pressure-increase linear valve 324 provided between the high pressure source 320 and the common passage 410 ; and a normally-closed pressure-reduction linear valve 328 provided between the common passage 410 and the master reservoir 414 .
  • a normally-closed front/rear cut-off valve 452 is provided on the common passage 410 .
  • devices such as the slip control device 400 and the linear valve device 322 are controlled based on instructions of the brake ECU 340 mainly constituted by a computer.
  • the common passage 410 corresponds to the upstream portion.
  • the manual cut-off valves 440 , 442 are closed, and the front/rear cut-off valve 452 is opened.
  • the linear valve device 322 is controlled in a state in which the master cylinder 430 and the hydraulic booster 432 are isolated from the common passage 410 , whereby a hydraulic pressure in the common passage 410 is controlled to control the hydraulic pressures in the respective brake cylinders 6 , 12 in common.
  • the hydraulic pressures in the respective brake cylinders 6 , 12 are controlled by the linear valve device 322 in common and are individually controlled by the slip control device 400 .
  • the hydraulic pressure in the common passage 410 is controlled in the same manner as in the third embodiment.
  • a current (Iopen+ ⁇ *) is supplied to the pressure-increase linear valve 324 .
  • a current (Iopen+ ⁇ *) is supplied to the pressure-increase linear valve 324 .
  • a current (Iopen+ ⁇ *) is supplied to the pressure-reduction linear valve 328 .
  • a current (Iopen+ ⁇ *) is supplied to the pressure-reduction linear valve 328 .
  • the stiffness in the upstream portion as the common passage 410 is reduced as described above. Accordingly, it is possible to well suppress vibrations of the hydraulic pressure in the common passage 410 with operations of the pressure holding valve 200 and the pressure reduction valve 204 .
  • the hydraulic braking system may be configured as illustrated in FIG. 14 . It is noted that the same reference numerals as used in the first through fourth embodiments are used to designate the corresponding elements of this embodiment, and an explanation of which is dispensed with.
  • a hydraulic-pressure producing device 500 includes an electric motor.
  • the hydraulic-pressure producing device 500 includes a master cylinder 502 and an advancing-force control device 504 .
  • the master cylinder 502 includes two pressurizing pistons 506 , 508 and an input piston 510 coupled with the brake pedal 24 .
  • the input piston 510 is movable relative to the pressurizing piston 508 .
  • Front pressure chambers 512 , 514 are defined in front of the respective pressurizing pistons 506 , 508 .
  • the brake cylinders 6 , 12 are connected to the respective front pressure chambers 512 , 514 via the respective fluid passages 44 , 46 .
  • the slip control device 16 is provided between each of the brake cylinders 6 , 12 and a corresponding one of the front pressure chambers 512 , 514 .
  • the advancing-force control device 504 includes an electric motor 518 and a motion converter 520 .
  • the motion converter 520 converts rotation of an output shaft 522 of the electric motor 518 to linear motion to move an output member 524 linearly.
  • the motion converter 520 converts rotational power of the electric motor 518 to an advance force to transmit it to the pressurizing piston 508 .
  • Devices connected to a brake ECU 530 include the stroke sensor 230 and the wheel speed sensor 232 . Also, the electric motor 518 is connected to the brake ECU 530 via a drive circuit 532 .
  • the brake ECU 530 includes a motor controller 534 .
  • a current to be supplied to the electric motor 518 is controlled such that a hydraulic pressure in each of the front pressure chambers 512 , 514 is brought closer to a magnitude corresponding to a target hydraulic braking force.
  • the current to be supplied to the electric motor 518 is controlled, and the slip control device 16 is controlled.
  • the electric motor 518 is controlled to suppress vibrations of the hydraulic pressure in the respective front pressure chambers 512 , 514 .
  • the electric motor 518 may be controlled to reduce stiffness in each of the front pressure chambers 512 , 514 to suppress the vibrations.
  • a normally open valve may be used for the pressure increase valve.
  • the present invention is not limited to the details of the illustrated embodiments, but may be embodied with various changes and modifications, which may occur to those skilled in the art.
  • the present invention is also applicable to the configuration in which the pump device is operated in traction control or vehicle stability control.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transportation (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Regulating Braking Force (AREA)
  • Braking Systems And Boosters (AREA)
US14/902,664 2013-07-18 2014-05-12 Hydraulic braking system Active US9919687B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2013-149094 2013-07-18
JP2013149094A JP5947757B2 (ja) 2013-07-18 2013-07-18 液圧ブレーキシステム
PCT/JP2014/062609 WO2015008525A1 (ja) 2013-07-18 2014-05-12 液圧ブレーキシステム

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US20160200301A1 US20160200301A1 (en) 2016-07-14
US9919687B2 true US9919687B2 (en) 2018-03-20

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US (1) US9919687B2 (de)
EP (1) EP3023311B1 (de)
JP (1) JP5947757B2 (de)
KR (1) KR101728284B1 (de)
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WO (1) WO2015008525A1 (de)

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US11059342B2 (en) * 2017-09-19 2021-07-13 Jaguar Land Rover Limited Actuator system

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US9581254B2 (en) * 2014-08-21 2017-02-28 Toyota Jidosha Kabushiki Kaisha Pressure regulator and hydraulic brake system for vehicle equipped with the same
JP6747388B2 (ja) * 2017-06-28 2020-08-26 株式会社アドヴィックス 制動制御装置
JP6819550B2 (ja) * 2017-11-17 2021-01-27 トヨタ自動車株式会社 車両用制動力制御装置
JP7204502B2 (ja) * 2019-01-25 2023-01-16 株式会社アドヴィックス 制動制御装置
JP7234998B2 (ja) * 2020-04-17 2023-03-08 トヨタ自動車株式会社 液圧ブレーキシステム
KR20220081113A (ko) * 2020-12-08 2022-06-15 현대자동차주식회사 브레이크 패드의 마찰계수 예측을 이용한 제동 제어 방법

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JP2000159094A (ja) 1998-09-22 2000-06-13 Toyota Motor Corp 液圧ブレーキ装置
JP2009292176A (ja) 2008-06-02 2009-12-17 Toyota Motor Corp ブレーキ制御装置
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CN105408176B9 (zh) 2018-12-11
EP3023311A1 (de) 2016-05-25
KR20160018727A (ko) 2016-02-17
JP2015020518A (ja) 2015-02-02
JP5947757B2 (ja) 2016-07-06
US20160200301A1 (en) 2016-07-14
EP3023311A4 (de) 2017-05-03
EP3023311B1 (de) 2019-04-03
KR101728284B1 (ko) 2017-04-18
CN105408176B (zh) 2018-10-26
WO2015008525A1 (ja) 2015-01-22
CN105408176A (zh) 2016-03-16

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